| 1. |
- Ananías, Rubén A., et al.
(författare)
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Collapse of Eucalyptus nitens Wood after Drying Depending on the Radial Location Within the Stem
- 2014
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 32:14, s. 1699-1705
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Tidskriftsartikel (refereegranskat)abstract
- Collapse is almost certain to occur in the industrial drying of Eucalyptus nitens, and as such this prevents the lumber manufacturing industry in Chile from producing commercial solid wood products from this species. This problem is still unsolved, and different studies to reduce collapse are currently underway. In this exploratory study, shrinkage and collapse after drying of Eucalyptus nitens was measured for boards cut from different radial locations within the stem (core, transition and outer wood from pith to bark) and having different annual ring orientation (flat-sawn and quarter-sawn). Even though exploratory, the results appear to confirm that pieces that were cut from the center of the trees were less susceptible to collapse than the pieces cut from the transition zone between the center and the periphery. On average, collapse in transition wood was approximately 50% higher than the collapse observed in wood cut from the central zone of the trees.
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| 2. |
- Pérez-Peña, Natalia, et al.
(författare)
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Hygromechanical strains during the drying of Eucalyptus nitens boards
- 2016
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Ingår i: MADERAS. - 0717-3644 .- 0718-221X. ; 18:2, s. 235-244
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Tidskriftsartikel (refereegranskat)abstract
- Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards. Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer. The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0.18 mm/mm with a surface deformation of 0.20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0.11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.
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| 3. |
- Sepúlveda-Villarroel, Victor, et al.
(författare)
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The Development of Moisture and Strain Profiles During Pre-Drying of Eucalyptus nitens
- 2016
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 34:4, s. 428-436
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes one of a series of studies carried out at the University of Bio-Bio in Chile with the objective of characterizing the response of Eucalyptus nitens to drying. The ultimate goal is to minimize collapse and internal intra-ring checking in the industrial drying of Eucalyptus nitens, which currently prevents the lumber manufacturing industry in Chile from producing a large number of commercial solid wood products from this species. This study focuses, however, on the drying conditions that have been shown in previous studies and are known in the industry to minimize collapse and internal intra-ring checking. For these conditions, this study reports the development of moisture content and internal strain profiles during drying. In addition, a simple diffusion model based on the concept of the effective diffusion coefficient was proposed to compare the drying rates in the radial and tangential directions. The results showed that the diffusion coefficient in the radial direction was approximately 50% higher than that in the tangential direction. Internal strains, on the other hand, developed approximately at the same time, regardless of the annual ring orientation. This indicates that it would be feasible to apply strain relief strategies simultaneously to all boards regardless of their annual ring orientation in order avoid internal intra-ring checking during pre-drying. This finding could be used as a benchmarking tool in the industrial drying for solid wood products of Eucalyptus nitens.
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